I've had a strange problem that has occurred on two PC's, both lost their network key, my main pc just did it for the second time this morning while I was using it. The field isn't corrupted, it's blank. Re-enter the key and everything's fine. Both PCs are protected by Zone Alarm and anti-virus SW.

When you hook-up to your network, did you tell your computer to "remember" the network and automatically connect? I'm thinking it might be possible your router is dropping you for some reason and when it does, your computer does not auto-reconnect resulting in the need to put the network key in again. How is your signal strength on your machines?